(function (doc, win) {
    isIE();
    var docEl = doc.documentElement,
      resizeEvt = 'orientationchange' in window ? 'orientationchange' : 'resize',
      recalc = function () {
        var clientWidth = docEl.clientWidth > 750 ? 375 : docEl.clientWidth;
        if (!clientWidth) {
          return
        }
        docEl.style.fontSize = 100 * (clientWidth / 750) + 'px';
      };
    if (docEl.clientHeight < 504) {
      docEl.style.height = 504 + 'px';
    }
    recalc();
    if (!doc.addEventListener) return;
    win.addEventListener(resizeEvt, recalc, false);
    doc.addEventListener('DOMContentLoaded', recalc, false);
    function isIE(){
        var userAgent = navigator.userAgent;
        var reIE = new RegExp("MSIE (\\d+\\.\\d+);");
        reIE.test(userAgent);
        var IEVersion = parseInt(RegExp["$1"]);
        if(IEVersion<9){
          alert('您的浏览器太老啦，请更新后再来吧~')
        }
      }
    })(document, window);